Rock boring machine having driven rotors with swinging hammers

ABSTRACT

A rock boring machine utilizing a cutting head in the form of at least one rotor carrying rock breaking hammers pivotally mounted on the rotor to swing freely between end stops. The rotor is mounted on the end of a forwardly projecting rotatable shaft supported on a rigid frame and the axis of the rotor is inclined to the axis of the shaft at an angle of less than 80*. Independent drives are provided for the rotor and shaft and the cutting head is adapted to bore a hole which will accommodate the whole machine.

United States Patent [191 Taylor Assign tier Africa [22] Filed: July 26, 1971 [21] Appl. No.: 165,904

[30] Foreign Application Priority Data July 31, 1970 South Africa 5311 [52] US. Cl 299/56, 299/33, 299/62 [51] Int. Cl E01q 3/04 [58] Field of Search 299/31, 33, 56, 58, 299/62, 85, 86

[56] References Cited UNITED STATES PATENTS 1,659,942 2/1928 Carlson 299/58 Z2 Z6 3 2! G 33 25 1 i 1 Oct. 16, 1973 1,195,396 8/1916 Recen 299/86 2,466,709 4/1949 Karr 299/58 X 2,827,274 3/1958 Poundstone 299/58 X FOREIGN PATENTS OR APPLICATIONS 609,860 2/1935 Germany 299/58 Primary Examiner-Ernest R. Purser Attorney-Stevens, Davis, Miller & Mosher [5 7] ABSTRACT 13 Claims, 5 Drawing Figures llllllllllllllllllllll a l i i Patented Oct. 16, 1973 2 Sheets-Sheet 1 I 1 24 22 31 14 as 32 33 38 10 I! 13 IO I2 Patented Oct. 16, 1973 3,765,725

2 Sheets-Sheet 2 ROCK BORING MACHINE HAVING DRIVEN ROTORS WITH SWINGING HAMMERS This invention relates to rock boring machines of the type used in mining or tunnelling operations to cut a tunnel through hard rock.

Machines for tunnelling in hard rock are today almost exclusively confined to heavy machines using rams to anchor them in position and to apply the high thrust required for their working heads to break the rock.

It is the object of the present invention to provide a rock boring machine which is mobile and of light weight compared with presently available types.

According to this invention there is provided a rock boring machine comprising a rigid frame supporting a forwardly projecting rotatable shaft carrying a cutting head in the form of at least one rotor independently rotatable about an axis inclined to the axis of the shaft at an angle of less than 80 and having rock breaking hammers pivotally mounted thereon to swing freely between end stops located on the rotor assembly.

Further features of the invention provide for the rigid frame to be a chassis, for the chassis to be wheeled, for the axis of at least the outer rotors to be off-set from the axis of the shaft so that the axes of the rotor and of the shaft will not intersect, and for the shaft and cutting head to have independent power supplies.

A preferred embodiment of this invention will be described below, by way of example only, reference being made to the accompanying drawings in which:

FIG. 1 is a side view of a rock boring machine in use, showing two cutting rotors mounted on a cutting head;

FIG. 2 is a plan view of the same machine in use, with the outlines of four cutting rotors;

FIG. 3 is a sectional elevation of the rock boring machine along line AA in FIG. 2;

FIGS. 4 and 5 are diagrams of one cutting rotor and part of the tunnel to illustrate certain important relationships between the axes and the radii of the tunnel and at least one of the rotors.

In this embodiment of the invention, a rock boring machine includes a chassis 1 supported by a pair of front wheels 2 and a pair of rear wheels 3. The wheels are outwardly inclined to provide stability to the chassis 1 when the machine is located in a tunnel. Each of the front pair of wheels 2 is conveniently power driven in this example by an hydraulic motor 4 suitably located under the chassis 1. The speed of the motor 4 and consequently of the wheels 2 is controlled by means of a conventional control mechanism mounted on the chassis in a console 5 (as shown in dotted lines). The driving system is designed to not only move the equipment supported by the chassis l but also to provide an adequate thrust for a cutting head 6 located at the front of the machine.

A further wheel 7 is preferably, but not essentially, mounted at the rear of the machine to counteract any tendency of the front of the machine to tip downwardly during use. The wheel 7 is arranged to allow for the vertical adjustment thereof relative to the chassis 1. For this purpose, the wheel may be rotatably mounted with its axle forming a common journal for one end of an arm 8 and the free end of the piston of a jack assembly 9, both of which are also pivotally mounted on the chassis 1. The vertical movement provided by means of the jack 9 will enable the wheel to negotiate roughness of the ceiling of the tunnel while still maintaining an adequate pressure thereagainst.

The chassis 1 supports, in suitable bearings 10, a longitudinal forwardly projecting shaft 1 1 carrying the cutting head 6 at the front end thereof. At least one of the bearings is also adapted to transmit the axial thrust from the chassis 1 to the cutting head 6. The shaft 11 is driven by an hydraulic motor 12 and by a chain transmission 13 constructed to reduce the speed of rotation of the shaft 11. v

The cutting head 6, in this example, comprises a frame 14 having rotatably mounted thereon two cutting rotors 15. These rotors have their axes of rotation inclined to the main shaft axis 16 as shown in FIG. 1. Provision is made for the installation of another pair of reaming rotors 17 as shown in dotted lines in FIG. 2. The rotors 15 are arranged to be driven by a single hydraulic motor 18 independently of the motor 12 for the main shaft 11. The rotors 17 can more conveniently be driven by further separate motors.

The fluid supplies 18a for the hydraulic motor or motors driving the rotors 15 and 17, cooling and dustabating water for the cutter head and any necessary control signal transmitting means for the cutting head 6 are passed through suitable passages formed in the main shaft 11. The fluid supplies, being pressurized, enter the shaft 11 via a bank of hydraulic slip rings 19. The returning low pressure fluid is received by the slip rings 19 in a similar manner. The signal transmitting means may be electrical conductors, in which case the signals are transmitted and received by a bank of electric slip rings 20.

Each cutting rotor 15 has a plurality of hammers 21 disposed about its periphery. The hammers 21 are capable of swinging freely and are adapted to extend outwardly under the influence of centrifugal force upon rotation of the rotors l5.

The preferred design of a rotor is such that when the hammers strike the rock, no shock load is thrown back onto the hammer pivot. To obtain this desired effect each hammer is pivotally secured to the rotor at one end. The center of gravity of the hammer is eccentric to the pivot and allows a combination of both radial and rotational movement of the striking tip relative to the axis of rotation of the rotor. The design characteristics of the hammers are achieved by ensuring that the distance of the striking tip from the pivot'is equal tothe (radius of gyration) divided by the distance between the pivot and the center of gravity. A detailed disclosure of such a hammer is given in our U.S. Pat. No. 3,695,724.

It is also desirable that all the energy given up by the hammer in striking the tool is restored to the hammer 1 by the centrifugal force applied thereto during the remaining portion of the revolution of the rotor in order to bring the hammer back into the striking position just at the correct time to strike the rock. This characteristic can seldom be attained and from a practical point of view it is necessary to use shock absorbers 21A to limit the swing of the hammers in both directions.

In this example where two rotors 15 are used, both rotors 15 are inclined to the main shaft axis 16 and have their axes 22 parallel. The rotors 15 are oppositely disposed about the main shaft axis 16 such that one complete revolution of the main shaft 11 will cause the whole area of the rock face 23 to be cut. For this purpose, one rotor 24 is adapted to cut an outer portion 25 of the area and the other rotor 26 the inner portion 27. The inner front edge 28 of the rotor 26 adapted to cut the inner area 27 of the rock face 23 lies substantially on the main shaft axis 16 which axis is also the axis of the tunnel. The foremost edge 29 of both rotors 15 is adapted to out along substantially the same path on the rock face and is arranged to project forwardly of the shaft by the same amount.

It has been found from practical tests that optimum rock breaking conditions are obtained when the hammers strike the rock at a point at or close to the point on the rock face such that a line drawn from this point to the axis of the rotor is at right angles to the direction of traverse of the rotor.

FIG. 5 shows schematically a section of the tunnel taken at right angles to the direction of the axis of the rotor 24 adapted to cut the outerarea 25 of the rock face 23. It will be seen that the diameter and the inclination of the rotor 24 is of importance when designing the machine. If r is the radius of the rotor 24, R is the radius of the tunnel and a is the inclination of the axis of the tunnel as shown in FIG. 4, then the relationship r/R cosine or results.

If there is no forward feed of the machine the profile of the tunnel section in FIG. 5 would be a perfect ellipse as shown by the solid line.

Due to the normal forward feed of the machine, the profile of the tunnel in FIG. 5 varies from that of a perfect ellipse in the zone marked by the dotted line. It is this zone of rock which is being hammered and broken off by the hammers 21 on the rotor 24.

To ensure that the hammers 21 strike the rock at the optimum point, it is advisable to make the ratio r/R less than cosine 01 and/or to offset the axis of the rotor 24 from the axis 16 of the main shaft 1 1. If this is not done, the rotor 24 will work inefficiently since the hammers may strike the rock at two points on the rotor periphery, this can be clearly seen from FIG. 5 by imagining a rotor of radius greater than the radius of curvature of the end of the ellipse.

The offset should be in the direction of the striking of the hammer blows. This limiting design factor applies particularly to those rotors which cut the periphery of the tunnel, thus the reaming rotors 17 would also be subject to this limiting factor but cutting rotor 26 for the inner area of the rock face would not be subject to it.

Since both the main shaft 11 and the rotors and 17 rotate about the main shaft axis 16, the rotor 26 will have less volume of rock to break, because it operates on a smaller radius about the axis 16, than rotor 24. To allow for such variation the number, shape, weight and spacing of the hammers may be varied to suit the particular conditions.

It will be appreciated that the reaction of motor 12 and drive 13 will tend to rotate the chassis 1 in the opposite direction to that of the cutting head. Due to the.

small reaction forces involved in the rock breaking process, the torque required to rotate the head is not great and this can be counteracted by distributing the various items of equipment on the chassis, so that the center of gravity of the machine is sufficiently off-set from the axis 16 of the main shaft 1 1. If required, additional balance weights 30 in the form of bars, rails or the like can be added to the side of the chassis to obtain. additional counter torque. Another method of countering the torque which can be used either alone or in conjunction with the off-setting of the center of gravity isto set two or more of the wheels at a slight angle to the axis of the tunnel and thus steer the machine against the reaction torque.

. The frame 14 of the cutting head is provided with a rock extraction mechanism which in one form comprises radially extending vanes 31 adapted to push rearwardly the debris falling on the tunnel floor from the working face 23. The vanes are inclined to a plane transverse of the machine and operate upon rotation of the cutting head 6.

A shield 32 secured to the shaft 11 in front of the chassis 1 but at-the rear of the head 6, is adapted to rotate therewith, and simultaneously act as a lifting means for the debris. Scoops 33 are attached to the front face of the shield 32 to lift the debris pushed rearwardly by the vanes 31. The scoops 33 lead into passages 34 through the shield 32 located to discharge onto a conveyor belt 35 supported by a chassis l. The conveyor belt 35 is adapted to transport the debris to the rear of the machine where it is deposited on suitable removing means.

Preferably the edge 35A of the shield will be of flexible material so that the shield can closely follow any irregularities formed in the wall of the tunnel during cutting operations.

The passage 34 through the shield 32 would be so arranged as to prevent, as far as practicable, the dispersion of dust in the general body of the air.

Still further, to reduce the risk of dust in the general body of the air, it might be preferred to arrange for the air close to the working face 23 to be at a slightly lower pressure than that in the rest of the tunnel. Such a condition can be brought about by arranging for a fan to suck air through a non-rotating shield 37 (shown in FIG. 1) or alternatively sucking air through the shield 32 by means of a duct 38 with a suitable rotating seal (as shown in FIG. 2). The dusty air would be led away through a ventilation pipe in the tunnel for disposal or treatment.

In use, both the main shaft 11 and the cutting rotors 15 rotate simultaneously about their respective axes to cut a tunnel of circular cross-section; the main shaft 11 and consequently the cutting head 6 rotates considerably more slowly than the rotors.

It will be realized that the profile of the cut at the working face 23 will depend on the positions of the rotors l5 and also on the sizes and spacings of the hammers 21. A typical profile is shown in FIG. 1. The crosssectional shape of the tunnel, normally circular, can be varied by varying the position of the shaft 11 with the cutting head 6 relative to the center of the tunnel. For

. instance, reciprocating the shaft cutting head up and down at suitable intervals would produce a quasieliptical tunnel section more accurately described as a rectangle with a semi-circle above and below it. Jacks may be provided for this lifting and lowering purpose. Such a cross-section would be of particular use in places such as very deep mines, where the shape of the tunnel is important from the rock stress aspect or in sewers and other tunnels close to the surface, where space may be limited.

In small diameter tunnels there may be space for only one cutting rotor in which case the rotor 26 would be eliminated and rotor 24 extended so that its inside row of hammers 21 would cut close to the center of the working face.

It is possible to convert a medium size machine using two rotors to cut larger diameter tunnels by adding one or more reaming rotors (as shown in dotted lines) to the cutting head 6. Certain other simple modifications would be required to the debris collecting mechanism and to the positioning of the shaft 11 relative to the wheels 2 and 3.

In order to ensure that the machine is operating at the best combination of speeds of rotation of the cutting rotors 15, cutting head 6 and forward travel (imparted by the power driven wheels 2) various monitoring devices would be fitted and the leads from those on the cutting head would be led through the bearings 10 to the bank of slip rings 20 and thence to a console which could be conveniently situated at 5. The console would indicate to the driver the degree of correct function of the various sections of the machine and would automatically or manually control these functions.

Should there be sufficient space, the power pack producing the hydraulic power can also be placed in the zone of the console.

The above description is of a preferred design, but a number of variations and additions are possible without departing from the scope of the invention. For instance, the axes of the rotors need not be parallel and steering facilities may be built into the chassis. Also the drives may be by a power medium other than hydraulics and there could be a door in lifting shield 32 to allow access to the cutting head for maintenance purposes. Provision can be made for a protective canopy for the operators.

Finally, it is to be understood that the machine may be used in other ways than that described above. For example, the machine may be modified and mounted on a frame without wheels for use in steep or vertical hole boring. When such operations are conducted downwardly more sophisticated rock extraction equipment than that referred to above will usually be required and if used for raise boring, the rotors will have to be arranged to allow a lifting cable or rod to pass between the rotors and be suitably secured to the frame or main drive shaft.

Also in the boring of large diameter tunnels where considerable space is available more rotors can be used than the four shown in the preferred embodiment above. The location of these additional rotors and their hammer assemblies will all be designed to maintain, as far as reasonably possible, a uniform breaking operation for all rotors. This arrangement could enable standard rotors to be used for various tunnel diameters and thus avoid large rotors with their inherent repair and maintenance difficulties.

What I claim as new and desire to secure by Letters Patent is:

l. A rock boring machine comprising a rigid frame supporting a forwardly projecting rotatable shaft and first means for driving the shaft, said shaft carrying a cutting head having at least one rotor independently rotatable about an axis inclined to the axis of the shaft at an angle of less than the rotor having second means associated therewith for driving said rotor independently of the shaft about the axis of rotation of said rotor and rock cutting hammers pivotally mounted on said rotor to swing freely between end stops located on the rotor.

2. A rock boring machine as claimed in claim 1 in which the axis of at least one rotor is off-set from the axis of the shaft.

3. A rock boring machine as claimed in claim l including a shield with an edge of flexible material supported behind the cutting head and of a size to fit closely within a hole made by the cutting head.

4. A rock boring machine as claimed in claim 1 including a rock extraction mechanism located adjacent the cutting head and a discharge conveyor adapted to receive cut rock from the extraction mechanism.

5. A rock boring machine as claimed in claim 1 in which the cutting head includes a pair of rotors oppositely disposed around the shaft and with their axes inclined and off-set from the axis of the shaft.

6. A rock boring machine as claimed in claim 5 including further rotors arranged about the shaft and located radially outwardly of and rearwardly of the pair of rotors.

7. A rock boring machine as claimed in claim 6 in which the further rotors are symmetrically arranged about the shaft and adapted to operate to give an equal rock breaking load to each rotor.

8. A rock boring machine as claimed in claim 6 in which the rotors have different numbers of hammers mounted thereon.

9. A rock boring machine as claimed in claim 1 in which the rotor is driven through a hydraulic motor and the shaft through a separate motor and drive assembly.

10. A rock boring machine as claimed in claim 9 in which the power supply to the rotor motor is passed through the shaft.

11. A rock boring machine as claimed in claim 1 in which the frame is a mobile chassis.

12. A rock boring machine as claimed in claim 11 in which the chassis has an upwardly projecting pivotally mounted and resiliently supported stabilizing boom .adapted to contact the wall of a hole cut by the machine above the chassis.

13. A rock boring machine as claimed in claim 12 in which the chassis is mounted on wheels driven by hydraulic motors and the boom carries a free running wheel at its upper end. 

1. A rock boring machine comprising a rigid frame supporting a forwardly projecting rotatable shaft and first means for driving the shaft, said shaft carrying a cutting head having at least one rotor independently rotatable about an axis inclined to the axis of the shaft at an angle of less than 80*, the rotor having second means associated therewith for driving said rotor independently of the shaft about the axis of rotation of said rotor and rock cutting hammers pivotally mounted on said rotor to swing freely between end stops located on the rotor.
 2. A rock boring machine as claimed in claim 1 in which the axis of at least one rotor is off-set from the axis of the shaft.
 3. A rock boring machine as claimed in claim 1 including a shield with an edge of flexible material supported behind the cutting head and of a size to fit closely within a hole made by the cutting head.
 4. A rock boring machine as claimed in claim 1 including a rock extraction mechanism located adjacent the cutting head and a discharge conveyor adapted to receive cut rock from the extraction mechanism.
 5. A rock boring machine as claimed in claim 1 in which the cutting head includes a pair of rotors oppositely disposed around the shaft and with their axes inclined and off-set from the axis of the shaft.
 6. A rock boring machine as claimed in claim 5 including further rotors arranged about the shaft and located radially outwardly of and rearwardly of the pair of rotors.
 7. A rock boring machine as claimed in claim 6 in which the further rotors are symmetrically arranged about the shaft and adapted to operate to give an equal rock breaking load to each rotor.
 8. A rock boring machine as claimed in claim 6 in which the rotors have different numbers of hammers mounted thereon.
 9. A rock boring machine as claimed in claim 1 in which the rotor is driven through a hydraulic motor and the shaft through a separate motor and drive assembly.
 10. A rock boring machine as claimed in claim 9 in which the power supply to the rotor motor is passed through the shaft.
 11. A rock boring machine as claimed in claim 1 in which the frame is a mobile chassis.
 12. A rock boring machine as claimed in claim 11 in which the chassis has an upwardly projecting pivotally mounted and resiliently supported stabilizing boom adapted to contact the wall of a hole cut by the machine above the chassis.
 13. A rock boring machine as claimed in claim 12 in which the chassis is mounted on wheels driven by hydraulic motors and the boom carries a free running wheel at its upper end. 